Reordered file into more logical sections
Taken code out of addVariableMap() into function agentList() for reuse
Extended the addTransition() interface to allow left side agents
Kill gateway process from destructor rather than using die_on_exit

This is because with my hack to py4j the die_on_exit method doesn't
work because of the redirection of the stdout. In any case, this is
probably a neater method.